The question for any psychological determinist is where does logical, as opposed to causal, necessity come from? It certainly isn't given in any possible experience.

So, if logical necessity is a product of the human mind only, then the laws of our thought (e.g. the law of non-contradiction) have no application to the outside world, and are simply contingent on the physiological make-up of the brain.

Well, there goes physics then. F=ma, E=mc2, etc, are not features of the world, but are simply contingent descriptions based on our neural wiring.

For scientific knowledge to exist, there must be a free will in the sense of a knower outside the stream of causal events. Maybe not a moral free agent, who can insert himself into the causal stream to perform something out of his own will, but definitely a process of mind above and beyond nature.

Even if the essence of free will is non-existent, you still have so many choices to make throughout your day and in your life, that effectively the appearance of free will is observed. The concept of free-will is actually irrelevant, if you choose to live a deterministic way of life, then you will fail because you will end up choosing the consequence of the actions of your non-free will. If you choose to life your life in an arbitrary way, where you are free to make any whimsical choice you desire, you are still subject to the consequences of those choices. Therefore, free-will is irrelevant, but rather having enough foresight to see how deep your choices can be to achieve a favorable outcome.

Chess, I believe is a perfect system that illustrates the illusion of free choice as a function of the myriad of choice one can make in such a closed system to achieve the outcome of only 3 states, checkmate, get checkmated, or draw. Millions upon millions of choices, possibilities, and permutations, but ultimately 3 possible consequences.

Computers can learn and make their own decisions and change their own programming. Not only that, the results of even a simple computer program can be impossible to predict advance--it happens every time you use Excel to generate a random number.

These capabilities are not new, either.

@YoungHegelian:

F=ma, E=mc2, etc, are not features of the world, but are simply contingent descriptions based on our neural wiring.

As a lifelong student of physics I would say, yes, obviously. Our "laws" do not bind the universe, and atoms don't know how to do calculus or solve differential equations. Scientific laws are only ever approximations, some exceedingly good.

For scientific knowledge to exist, there must be a free will in the sense of a knower outside the stream of causal events.

Why? How does knowledge exempt you from cause and effect?

@Matteo:

Therefore a computer analogy tells us nothing whatsoever about why we are conscious, and therefore (one would think) about free will.

A computer is not conscious, and its behavior (ideally) is completely deterministic. Yet it is capable of making its own decisions and changing its own programming. "Deterministic" doesn't mean what people think it does; your actions may be completely deterministic and yet give an appearance of "free will" convincing even to yourself.

Even assuming complete determinism, and complete knowledge of the state of every part of your nervous system, it would be physically impossible to predict the future state of your nervous system for more than the barest fraction of a second ahead.

Likewise, without free will you could still be conscious; it would just mean that your thoughts are determined as well your actions. Free will and consciousness don't have to go together.

The Free Will in a person's soul is the only reason to have laws to restrain murder, slavery, abortion, false imprisionment, torture and Communism. All the Social Darwinists and the Plain Old Materialist Darwinists are as usual wrong from the get go. Control over men's free will is their Raison D'etre. If there were no free will, then why have all European and American governments tried to control men's minds 24/7 since 1900?